A service for providing useful information to a user in consideration of a current geographical position of the user is generally referred to as a location-based service.
A core system for the LBS is a positioning system which measures a positioning value of a target object using wired/wireless communication technology.
That is, a purpose of the positioning system is to reduce a difference between the measured positioning value and an actual positioning value of the target object so as to enhance user experience of the user using the LBS.
When a driver forgets a position of a vehicle after parking the vehicle in a parking lot, the position of the vehicle may be detected using a remote control key having a function of opening/closing a door or a function of generating a sound through a speaker. However, such a method may not provide a correct direction and distance to the vehicle.
In order to overcome this limitation, global positioning system (GPS) modules may be installed in a vehicle-mounted device and a parking position detecting device respectively so as to indicate a distance and a direction between both the devices. In the case of using a GPS which is a location-based positioning system, a GPS satellite emits electric waves toward the earth, and a GPS receiving device calculates a distance on the basis of a time taken for a signal transmitted from the satellite to arrive at the receiving device with reference to the electric waves.
According to a positioning method using the GPS, the position of the target object is calculated by applying a triangulation technique on the basis of distances between four or five satellites and the receiving device. However, due to straight propagation of the electric waves, the receiving device is able to communicate with the satellites only when visibility is maintained between the satellites and the receiving device. Therefore, positioning is difficult in an indoor environment.
In order to overcome this limitation, a WiFi positioning system (WPS) using a wireless LAN may be adopted. According to this system, a position is detected on the basis of received signal strength (RSS) measured in a user terminal with respect to a GPS module and a WiFi access point (AP). That is, when the GPS module is unable to obtain parking position information of a vehicle, the parking position information of the vehicle is obtained through WPS communication.
According to this technology, a parking position of a vehicle is detected through a mobile communication terminal and a short-range communication module of the vehicle. However, there occur a lot of errors in WiFi received signal strength indicator (RSSI) measurement in an iron-framed vehicle. Furthermore, when a WPS AP database based on a WiFi RSSI value is used, the accuracy of positioning is degraded.
Moreover, according to this technology, a GPS module and a WiFi module of the mobile communication terminal should be kept turned on. However, considering that users of mobile communication terminals turn on GPS modules and WiFi modules only when necessary, the users may experience inconvenience to additionally activate functions of the mobile communication terminals in order to use position tracking functions.